The report presents the results obtained during the commissioning the Electron Cooling System (ECS) of the Booster (Fig. 1), the first in the chain of three synchrotrons of the NICA accelerator complex. The work was performed without an ion beam and with a circulating ion beam He¹⁺ and ⁵⁶Fe¹⁴⁺. In the work with a circulating ion beam He¹⁺, the effect of reducing the lifetime of the circulating ions was observed when the velocities of the cooling electrons and the cooled ions coincide. The dependences of the electron beam current on the ECS parameters for different electron energy values were experimentally obtained. The specific features of operation of electron gun of the NICA Booster are hollow beam formation and the phenomenon of virtual cathode creation confirmed both experiments and by numerical simulation. In conclusion section the results of first experiments on electron cooling of ⁵⁶Fe¹⁴⁺ ion electron cooling are presented.